Fleeting habitats: Vernal pools essential to species survival

The reflective pools of water that surround low-lying trees on the side of the road right after spring’s snowmelt are more than pretty. In fact, they are an essential part of the ecosystem for any number of critters and creatures in Wilton’s woods.

These temporary bodies of water, known as vernal pools, are isolated wetland areas, says Sarah Breznan, the education coordinator of Woodcock Nature Center.

“Vernal pools are land form depressions that temporarily fill with water following heavy rainfalls and snowmelt in the spring — with vernal meaning spring. They can vary in size, shape and depth, and usually dry up by the middle of the summer. Vernal pools are considered ‘isolated’ wetlands because they are not permanently connected to other water bodies,” she said.

Unlike small ponds, the isolated nature of a vernal pool allows for the growth of small native amphibians that would otherwise be “preyed upon or out-competed.”

“The ephemeral nature of these pools ensures that fish cannot exist,” she said. In turn, “the lack of fish is essential to the life cycle of native amphibians.”

Woodcock Nature Center itself is full of vernal pools, as was evident when Ms. Breznan brought The Bulletin on a brief tadpole collection hike. During a hike of only a few minutes, the education coordinator was able to scoop tadpoles and frog eggs from vernal pools — and even pointed out a garter snake slithering on top of one of the water bodies.

While many species of animal use vernal pools for various reasons, a number of animals are completely reliant on the water bodies.

“Vernal pools provide shelter, food and nursery habitat for a great number of invertebrate, amphibian, reptile, bird, and mammal species,” Ms. Breznan said. “But some species are critically dependent on vernal pools and are unable to successfully complete their life cycle without them. … The eggs are laid in the pools where they are safe from fish. Here they will hatch, complete the aquatic tadpole stage, and emerge as terrestrial adult frogs and salamanders before the pools dry up in the late summer.”

At Woodcock, vernal pools are essential to the local environment.

“They are a sign of a healthy environment, biodiversity, and a healthy amphibian population,” she said. They are also “a good source of educational opportunities as we encourage visitors and campers to explore the pools and learn more about their local environment.”

Yet vernal pools will be a permanent mainstay of Connecticut only so long as residents make an effort to ensure their healthy survival.

“Vernal pools can be easily disturbed or destroyed by habitat loss, habitat fragmentation, changing water chemistry due to contaminated runoff like runoff containing sediments, garbage, road salt, oil, pesticides, herbicides, and a whole mixed bag of other household and industrial chemicals,” Ms. Breznan said.

So the next time you think about throwing that fast food bag out the window, think twice about the effect those leftover fries might have on the habitat of Connecticut’s amphibian species.